As is well known to those skilled in the art, gases such as acid gases (typified by hydrogen sulfide, carbonyl sulfide, carbon dioxide etc) may be removed from gas streams in which they occur by a wide variety of absorption processes. In these processes, the gas stream is contacted in an absorber with a lean liquor, in which the gas is soluble; and the gas is separated from the liquor in a desorber or stripper. The regenerated solvent is then recycled to the absorber.
The solvents which may be employed include chemical solvents such as diethanolamine, N-methyldiethanolamine, or tropine or physical solvents such as methanol; pyrrolidone; tetrahydrothiophene-1,1-dioxide; polyethylene glycol dimethyl ether; etc.
One commonly used system is the Selexol process in which polyethylene glycol dimethyl ether is used to absorb hydrogen sulfide, carbon dioxide, carbonyl sulfide, etc. from gas streams. Another common system is the Rectisol process which may be used for example to recover carbon dioxide by absorption in methanol.
The rich pressurized liquid from the absorber, typically containing methanol and carbon dioxide, is commonly depressurized in a flash drum to separate gas; the flashed liquid may then be heated and passed to a stripper wherein additional gas is separated. The lean absorbent is then recycled to the absorber.
It is well known to those skilled in the art that the separation of gas from the rich liquid is costly both in terms of capital expense (requiring flash drums, distillation towers, and heat exchangers) and operating expense (due to cost of pumping, heating, condensing, etc).
It is an object of this invention to provide a process for separating gases. Other objects will be apparent to those skilled in the art.